Tensiometer control system



Aug. 6,1940. w. s. COOK TENSIOMETER CONTROL SYST EII 2 Sheets-Sheet 1 Filed Ray 25, 1938 E E N INVENTO'R Willard 6. Cook.

Au 6, 194 0. w G, @0 2.210.708

mvsxougimi cou'moz. sYs'rsu v Filed llay 25. 1938 2 Sheet -Sheet 2 WITNESSES: INVENTOR WzZ/aka a 000k.

Patented Aug. 6, 1940 UNITED s'rA'rss PATENT. OFFICE 2,210,108 I rsssronm'rsn oon'raor. srsTs'M Willard 4G. Cook, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May as, mass, Serial No. 209,515 12 Claims. (on. 80-35) 'tothe strip as it passes between adjacent roll stands by a tensioning roller member applying tuting apparatus therefor which is of more simple construction,

Another object of my invention is toprovide a tension control system for astrip rolling mill which has a minimum of operating parts, which is simple in operation, and which is inexpensive to manufacture, install and maintain.

These and other objects and advantagesof my invention will be apparent from the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic viewof a tension :control system embodying the principal features of my invention, and

Figs. 2, 3 and 4 are diagrammatic views of modifications of that partof the control system shown in Fig. 1 whichprovides the proper energization for the booster generator. 7

In carrying out my invention I provide a booster generator in the field circuit of the roll stand 'motor and control the motor speed by exciting the' boostergenerator with a current of a polarity and value dependent upon the direction and amount of deflection oi the strip from a predetermined position. Alternative systems for providing the desired booster generator excitation are provided, using a variable ratio transformer principle or a resistance potentiometer 5o principle.

Referring now to Figure 1 of the drawings, a strip of material 6 such as steel is shown passing between two adjacent reducing roll stands land ll in the direction indicatedby the arrow. The rolls of the roll stand 8 are driven by a motor I! and rolls-of the roll stand l are driven by a motor I, the motor It being controlled by any suitable controller as shown and having a series field winding I and a shunt field winding l8. Energization 01' the shunt field winding l8 of 5 the motor I! is provided by connecting the shunt field winding to any suitable source of direct current power ofsubstantially constant potential represented by the conductors X and Y. This energizing circuit extends from con- 10 ductor K, through conductor 20, rheostat 22, conductor 24, field winding I8, conductors 26 and 28, the armature of a booster generator 30 and conductor 32 to the conductor Y. -The booster generator 30 is continuously driven at a substantially constant speed by any suitable motor 34 here shown as an alternating current motor connected to a source of alternating current power indicated by the conductors M, N and 0. It will be apparent that the speed of the motor I 4 may be varied by varying the current flow in its fleld winding ill by either adjusting the rheo- Stat 22 or varying the energization of the field winding'of the booster generator 30 to vary its voltage.

Tensioning of the strip 6 between the roll stands 8 and I0 is provided by causing a roller 36 mounted on an arm 38 to bear against the strip 6 and to deflect the strip from the normal pass line. The arm 38 has a pivotal mounting 40 and .has a connected arm 42 disposed'substantialiy horizontally and acted upon by a fluid pressure operated piston 44 in a fluidpressure cylinder IS. The tension applied to the strip 6 by the idling roller 36 is governed by the fluid pressure in the cylinder 46 and this pressure is maintained constant at a predetermined adjustable value by means of an adjustable pressure-regulating reducing valve 48 whose low pressure side is connected to the cylinder 46 and whose high pres 0 sure side receives air pressure from the air reser- 4 ,voir shown. The functioning of the piston operthe strip 6 by the idling roller 36 and to thus 50 'secure the proper tensioning of the strip 6, a

regulating means for controlling the speed of the roll motor I4 is provided and, in this instance, comprises a variable ratio transformer 50 having a secondary winding 52 and a primary winding 54.

. induced in the The primary winding 54 of the transformer 50 v is connected by conductors I6 and 88 to the phase conductors M and N oi the alternating current source of power represented by conductorsM.

N and O. The primary winding 54 of the transi'orm'er 5|! is'normally positioned at right angles to the secondary winding 52, and in this position causes no eiectromotive force to be induced in the secondary winding I2. The primary winding 54 is rotatable in eitherdirection with respect to the winding 52 to vary the coupling between the winding 52 and the winding !;l4 and to thus vary the amount of eiectromotive force.

induced in the secondary winding 52 The rotation oi theprimary winding 54 may be secured by mechanically connecting it to a gear ill by means oifla shaft 82, the gear {I engaging a rack '4 which isconnected to be I tor I2, field winding of booster generator conductor I4, the secondary winding 16 of a transformer I8, conductor 80, conductor 82, rectifier unit 84, conductor '88, rectifier unit 88 and conductor 90.

The rectifier units 84 and 88 are connected to pass opposite polarities of current in the circuit of the secondary winding 52. The rectifier unit 84 is connected to be shunted when the deflection of strip 6 increases beyond the predetermined normal amount represented by the positioning of the strip and its tensioning device in the drawing by the engagement of the movable contact element 92 which is supported tobe moved upon movement of the arm 38 bya supporting arm 94 with the fixed contact element 96 througlia circult which comprises conductor 82, conductor 80,

contact elements 96 and 92, and conductors 98 and86. A similar shunting circuit is provided for rectifier unit Bl comprising conductor 86,

conductor 98, movable contact element I82, con-- tact element I00 and conductors I02 and 90.

In the operation oi the device, with :the e1- ments or the device in the normal positions indicated by Fig. 1 of the drawings, the normal deflection of the strip is as indicated and theroll motor I is receiving sufilcient excitation to maintain a strip speed which will keep the strip in this normal degree of deflection, and under these normal conditions the booster generator 8|! is not excited and is. therefore, not eflecting 1 the excitation of theroll vmotor I4.-

.It, now, to any reason, the deflection oi the strip-6 sho d increase the relative movement of the primary and secondary windings 54 and 52 or variable ratio transformer 50 will cause an electromotiveforce to be induced in the secondary winding 52 having a value which is proportional to the amount of the relative displacement of the primary winding 54 from its normal position andthe engagement oi the contact element 82 with the contact element 96 will close the shuntingcircuit for the rectifier element 84,

permitting direct current impulses to flow in the circuit of the winding 52 and the field winding oi the booster generator in a direction such as to cause the booster generator 8| to generate a potential in the circuit or the field winding is of the roll stand motor I4 oi such polarity as to reduce the current flow in the field winding I8.

The reduction of the excitation of the motor I4 by the decrease in the current flow in its field winding I8 will cause the motor to inf crease its speed and to thus take up slack in the strip I and reduce itsdefiection. In this manner the system will operate to keep the deflection of the strip below a predetermined amount.

deflection oi the strip I decreases a predeterspeed of the roll stand motor I4 will be decreased to permit the deflection to return to normal .by means of the rotation of the primary winding 54 irom its normal position and the engagement of the contact elements 92 and S4 to provides shunting circuit for the rectifier element l8.

Anticipating circuits are provided for preventing hunting of the system and comprise a transiormer 10 whose primary winding .Il4-is conthe booster generator SI- and whose secondary winding 68 is connected in .the circuit oi'the field winding of the booster generator ll as herelnbeiore described. A transformer 18' has a.

primary winding I06 connected in parallel relation with the series fleld winding IQ of the roll motor I4 and a secondary .winding connected in the circuit of the field winding of the booster generator 30 as hereinbeiore described. With the primary winding "4 of the transformer I0 connected as described, it will be seen that any change in thepotential generatedby the booster generator 30 will cause a change in the current flow in the primary winding I04. and this change 7 in current'flow will cause an electromotive force to be induced in the secondary winding 68 of the transformer 10, In a like manner, any change in the current flow in the armature circuit of the roll stand motor I4 will cause a change in the potential (310p across its series field winding it which in turn will cause a change in the current flow in .theprimary winding I06 oi the In a like manner, when for any reason the I T mined amount below its normal deflection, the

nected' in parallel relation with the armature oi n'ansiormer l8, and the change in current flow in the winding I06 will cause an electromotive force to be induced in the secondary winding I6 oi the transformer I8.

The change in the generated potential of the booster generator 30 will be caused by the change in. its excitation and the change in the current flow in the armature of the roll stand motor- I4 will be caused by a change in its excitation; The secondary windings 68 and ii of the transformers Ill and 18 are so related with the circuit of the field winding of the booster generator 30 as to cause a decrease in the current flow in the fleld winding of the booster generator 30- when the potential of the booster generator '30 increases in one direction, and a'deorease in the current fiow of the field winding of the booster generator 30 when the potential of the booster generator 30 increases in the other direction. The secondary winding I6 oi the transformer II 4 is so related with the circuit oi the field winding of the booster'generator 30 as to cause a de-. crease in the current flow in thefield winding of the booster generator}! when the current flow in the armature oi-the roll stand motor I4 increases. Thus the anticipating circuits which include the transformer IO-and I8 will anticipate the changes to be made by the change in the excitation of the booster generator and will 2,910,708 decrease the degree of excitation of the booster generator 30 which causes these changes in advance of the actual changes to prevent the changes from varying from one extreme to another. Thus, before the speed of the roll stand motor I4 has been increased or decreased to prevent the. full correction of strip deflection necessary to return the deflection to the normal amount, the change. in the excitation of the motor M will be lessened to prevent the motor from overrunning or changing beyond its necessary final speed. In this manner, the anticipating circuits described will prevent hunting of the motor I I.

In Figs. 2, 3 and 4 there are shown modifications of part of the system of Fig. l in which different apparatus for securing the necessary changes in the excitation of the booster generator are provided. In these figures, the apparatus shown may be substituted for the analogous parts of the apparatus of Fig. 1, and similar parts have the same reference characters in the several figures.

Referring to Fig. '2, the auto-transformer 50' may be substituted for the variable ratio transformer 50 of Fig. 1, the other parts of the systact elements tem remaining the same. The autotransformer 50' is connected to a suitable source of alternating current through the conductors 56 and 58 and is provided with a series of taps to which a series of contact elements I08 are connected. A contact arm H is connected to gear 60 to traverse the series of contact elements upon movement of the gear 60 by changing deflection" of the strip as explained in the discussion ofthe system of Fig. 1, the contact arm causing the contact element 2 to traverse the series 'of conillt. The conductor 0; is .connected to substantially the middle ta'p of the auto-transformer 50' and in the normal position of the tensioning device, the contact element H2 engages the tap corresponding to this midposition so that in the normal position of the elements'there is no potential induced in, the circuit of the field winding of the booster generator 30. It will be seen that the same effects will be produced by this'auto-transformer operated as described as were produced by the variable ratio transformer 50 of the system of Fig. 1.

' In Fig. '3 there is shown a system in which a single rectifier 85 is connected in circuit with the field winding of the booster generator 30 and the secondary winding 56 of a variable ratio transfield winding of the booster generator 30 will depend upon the amount of deflection of the strip from its normal position and that the polarity of energization of the field winding of the booster generator 30 will depend upon the direction of the deflection of the strip from its normal position, and the booster generator will act accord- 66 of the circuit of the field winding of the booster generator 30, and which has a series of taps connectedto a series of contact elements M9. The contact element which is connected to the middle tap is normally engaged by a movable contact element III which is made to traverse the series of contact elements I09 by the gear Ii which is operated by the rack N as described in the connection with the discussion of the systems of Figs. 1 and 2.

In this system it will be seen that the amount of potential applied to the field winding circuit of the booster generator 30 will dependupon the amount of deflection of the strip from normal position .since the deflection governs the numher of contacts of the series of contacts I09 traversed by the movable contact 3. and the polarity of the potential applied to the field winding circuit of the booster generator 30 will be determined by the direction of the deflection of the strip from normal since the polarity of the potential drop between the mid point contact to which conductor 66 is connected and the taps above this mid point are opposite to the polarity of thepotential drop between this mid tap and the taps below the mid tap, as the circuit of the field winding of the booster generator is connected between these taps by the movable contact 3.

It is to be understood that the variable ratio transformers disclosed herein need not be the specific movable coil transformer or the autotransformer described, but maybe any transformer that will perform the. function'- of these 4 transformers in this system. A transformer whose ratio is varied by moving its core relative to both its prlmary'and secondary windings would perform the desired function equally as well as those described and it is to be understood that such a transformer is within the purview of my invention.

It will be seen that I have provided a system for maintaining a constant tension upon a strip of material as it is passing between adjacent reducing roll stands which will function to govern the speed of the driving motor of one of the. roll stands to maintain the deflection of the strip within predetermined limits and which is provided with an anticipating circuit for preventing hunting-of the driving motor which system has a minimum of operating parts and which is simple in operation andinexpensive to' manufacture, install and maintain.

In compliance with the requirements of the patent statutes, I have shown and described herein the preferred embodiments of my invention. It is to be understood, however, that the invention is-not limited to the precise constructions shown and described,- but is capable of modification by one skilled in the ,art, the embodiments herein shown beingmerely illustrative of the principles of my invention.

I claim as my invention: I

1. In a tandem strip rolling mill, tensioning means bearing upon the strip as it passes between adjacent roll stands of the mill subjecting the strip to a-tr'ansverse force to thus deflect and increase or decrease depending upon the amount.

4 of excitation oi said generator, and means controlled in accordance with the deflection of said strip by said tensioning means ior selectively exciting said generator with a polarity and with an amount of excitation dependent upon the di- 1 rection and proportional to the amount of deflection oi said strip irom a predetermined position.

2. In a device for maintaining tension on a length oi material as it passes between two work devices, tensioning means bearing on the length of material between the work devices and subjecting the length oi material to a transverse force to thus deflect and tension the length oi material, a variable speed motor connected to drive one of the work devices, electrical means for selectively varying the speed of said motor depending upon the polarity and degree oi energization of said electrical means, and means responsive to the deflection oi-said length of materialcior energizing said electrical means with a polarit and to a degree dependent upon the direction and degree of deflection oi said length of material irom a predetermined position, said means responsive to said deflection comprisinga continuously energized variable ratio transformer, rectifier means connected in circuit with the output side of said transiormer, means governed by the direction of deflection oi the strip from a predetermined position for selectively connecting said rectifier means to selectively govern the polarity of the rectifled output ofv said transformer and means controlled by the degree oi deflection of the strip irom said predetermined position for varying the ratio of said transformer.

3. In a tandem strip rolling mill, tensioning means bearing upon the strip as it passes between adjacent roll stands oi the mill subjecting the strip to a transverse force to thus deflect and tension the strip, alvarialile speed motor con-e nected in driving relation with the rolls oi one of the adjacent roll stands, a source of substantial! ly constant excitation for said variable speed motor, a continuously-driven generator connected to increase or decrease the excitation of said motor depending upon the polarity of the excitation of said generator, the amount oi said increase or decrease depending upon the amount oi excite.- tion of sid generator, and means controlled in accordance with the deflection oi said strip by said tensioning means ior selectively exciting said generator with a I polarity and with an amounitoi excitation dependent upon the direction and amount of deflection oi said strip irom a predetermined position, said means controlled in the deflection of the strip comaccordance with prising a continuously energized variable ratio transformer, rectifier means connected in circuit with the output side of said transformer and the fleld windingoi said generator, means governed by the direction of deflection oi the strip from a predetermined position for selectively connecting said rectifler means to selectively govern the polarity oi the rectified output oi said transiormer and means governed by the degree of deflection oi the strip from said predetermined position ior varying the,ratio of said transformer.

4. In a device for maintaining tension on a length of material as it' passes between two work devices, tensioning means bearing on the length of material between the work devices and subjecting the length of material to a transverse force to thus deflect and tension the length of material, a variable speed motor connected to drive one of the work devices, electrical means :10:

selectively varying the speed oi said motor depending upon the polarity and degree oi energization oi said electrical means, and means responsive to the deflection of said length oi materi al ior energizingsaid electrical means with a polarity and to a degree dependent upon'the'direction anddegree oi deflectionoi said length of material from a predetermined position, said means responsive to. the deflection oi the length of material comprising a variable resistor continuously energized from a source of direct current and having a movable contact element means connecting said electrical means in circuit with said resistor at a point intermediate the ends of the resistor and .with said movable contact element, means whereby the deflectionoi said length oi material governs the movement of said movable contact element, said movable contact element being so positioned as to engage said resistor at said point intermediate the ends oi the resistor when the length of material is deflectedto said predetermined position.

5. In a device ior maintaining tension on a length of material as it passes between two workdevices, tensioning means bearing on the length oi material between the work devices and subjecting the length of material to a transverse force to thus deflect and tension the length of material, a variable speed motor connected to drive one of the work devices, electrical means for selectively varying the speed of said motor depending upon the polarity and degree .oi' energization of said eelctrical means, and means responsive to the deflection of said length of material for energizing said electrical means with a polarity and to a degree dependent upon the direction and degree oi deflection of said length oi material irom a predetermined position, said means responsive to the deflection of the length of material comprising a continuously energized auto-transiormer having a series of taps intermediate the ends of its windings, a movable contact element for selectively engaging said taps, means ior moving said movable contact element in accordance with the deflection oi the length oi material, means connecting said electrical means in circuit with said movable contact element and with said transiormer at a point intermediate the ends oi said series oi taps, said movable contact element being so adjusted, as to engage the tap corresponding to the point oi connection of said electrical means to said transiorm'er when the length of material is in'said predetermined position, rectifier means in circuit with said transformer and said electrical means, and means responsive to the direction of deflection oi the length of material irom said predetermined position io'r selectively connecting said rectifier means to provide said polarity of energization ior said electrical means.

6. Ina tandem strip rolling mill, tensioning means bearing upon the strip as. it passes between adjacent roll stands oi the mill subjecting the strip to a transverse iorceto thus deflect and tension the-strip,- a variable speed motor connected in driving relation with the rolls of one oi the adjacent roll stands, a variable resistance other inaccordance with the diwhen the strip is deflected to the said normal position, and means whereby the excitation of said driving motor is varied inaccordance with the polarity and the amount of the potential drop between said predetermined point on said resistance element and said movable contact element.

'7. In a tandem strip rolling mill, tensioning means bearing upon the strip as it passes between adjacent roll stands of the mill subjecting the strip to a transverse force to thus deflect and tension the strip, .a variable speed motor connectedin driving relation with the rolls of one 01' the adjacent roll stands, a variable resistance element continuously energized from a direct current source and having a contact element movable along said resistance element, means whereby the said contact element is moved in one direction or the other in accordance with the directact element being so positioned as to occupy a tion and amount of'deflection of the strip from a predetermined normal position, said movable contact element being so positioned as to occupy a predetermined point on said resistance element when the strip is deflected to the said normal position and means whereby the excitation of said driving motor is varied in accordance with the polarity and the amount of the potential drop between said predetermined point on said resistance element and said movable contact element, said excitation varying means comprising a continuously driven generator having a field winding and having its armature connected in series circuit relation with the field winding of said driving motor, and a series circuit including said field winding of said generator and the portion 01 said variable resistance between said predetermined point and said movable contact eleby the said contact element is moved in one direction or the other in accordance with the direction and amount of deflection of the strip from a predetermined normal position, said movable conpredetermined point on said resistanceelement when the strip is deflected to said normal position, and means whereby the excitation of said driving motor is varied in accordance with the polarity and the amount of the potential drop between said predetermined point on said resist ance element and said movable contact element, said excitation varying means comprising a continuously driven generator having a fleld winding and having its armaturev connected in series circuit relation with the field winding of said driving motor and a series circuit including said field winding of said generator and the portion of said variable resistance between said predetermined point on said resistance element and said movable contact element, and means for producing in said series circuit a potential whose amount and polarity are proportional to and determined by the rate of change and the direction of change or the current in the armaturecircuit or said driving motor.

. 9. In a tandem strip rolling mill, tensioning means bearingupon the strip as it passes between tension the strip, a variable speed motor connected in driving relation with the rolls of one of .the adjacent rollstands, a variable resistance element continuously energized from a direct current'source andhaving a contact element movable along said resistance element, means whereby the said contact element is moved in one direction or the other in accordance with the direction and amountof deflection of the strip, said movable contact element being so positioned as to occupy a predetermined point on said resistance element when the strip is deflated a predetermined amount, and means whereby the excita-. tion of said driving motor is varied in accordance with the polarity. and the amount of the potential drop between said predetermined point and said movable contact element,-said excitation vary-' ing means comprising a continuously driven generator having a field winding and having its armature connected in series circuit relation with the field winding of said driving motor and a series circuit including said field winding of said generator and the portion of said variable resistance between said predetermined point and said movable contact element, and means for producing in said series circuit a potential whose amount and polarity are proportional to and determined by the" rate of change and the direction of change of the potential generated by said generator.-

10. In a tandem strip rolling mill, tensioning means bearing upon the strip as it passes between adjacent roll stands of the mill subjecting the strip to a transverse force to thus deflect and tension the strip, a variable speed motor connected in driving relation with the rolls of one of the adjacent roll stands, a variable resistance element continuously energized from a direct current source and having a contact element movable along said resistance element, means whereby the said contact element is moved in one direction or the other in accordance with the direction and amount of deflection of the strip, said movable contact element being'so positioned as to occupy a predetermined point on said resistance element when the strip is deflected a predetermined amount and means whereby the excitation of said driving motor is varied in accordance with the polarity and the amount of the potential drop between said predetermined point and said movable contact element, said excitation varying means comprising a continuously driven generator having a field winding and having its armature connected in series circuit relation with the field winding of said driving motor and a series circuit including 'said field winding ofsaid generator and the portion of 'said variable resistance element between said predetermined point and said movable contact element and means for producing in series circuit a potential whose amount and polarity are proportional to and determined by the rate of'change and the direction of change of the current in the armature circuit of said driving motor, and means for producing in said series circuit a potential whose amount and polarity are proportional to and determined by the rate of change and the direction of change of the potential generated by said generator.

11. In a tandem strip rolling mill, tensioning means bearing upon the strip as it passes between adjacent roll stands of the mill subjecting the strip to a transverse force to thus deflect and tension the strip, a variable speed motor connected in driving relation with the rolls of one of the -adlacent roll stands, a source-ofsubstantially 5 depending upon the polarity of' the excitation oi.

said generator, the amount of said increase or decrease depending upon the amount of excitation of said generator, means controlled in accordance with the deflection of said strip by said 10 tensioning means for selectively exciting said generator with a' polarity and with an amount of excitation dependent upon the direction and amount of deflection of said strip from a predetermined position, means controlled by the di- 15 rection 01' change and the rate of change of the current flow in the armature circuit of said driving motor for changing the excitation oi said gen-r erator in such a manner as to decrease the change in the excitation of said generator which is caus- 20 ingsaid change in the current in said-motor armature circuit, and means controlled by the direction of change and the rate of change of the potential generated by said generator for changing the excitation of said generator in such a 5 manner as to decrease the rate of change of the potential generated by said generator.

12. In a device for maintaining tension on a length of material as it passes between two work devices, tensioning means bearing on the length of material between the work devices and subjecting the length of material to a transverse force to thus deflect and tension the length of material, a variable speed motor connected to 6 drive one of the work devices, electrical means for selectively varying the speed, of said motor depending upon the polarity and degree of energization of said electrical means, and means responsive to the deflection of said-length of mal0 terial'ior energizing said electrical means with a polarity and to a degree dependent upon the direction and degree of deflection of said length of material from a predetermined position, said means responsive to said deflection comprising a 15 continuously energized transformer having relatively movable primary'and secondary windings for varying the transformer ratio, rectifier means connected in circuit with the output side ot said transformer, means controlled by the direction of 20 deflection of the strip from a predetermined position for selectively connecting said rectifier means to selectively control the polarity of tli rectified output 0! said transformer, and means controlled by the degree-of deflection of the strip from said 26 predetermined position for varying the relative positions of the windings of said transformer.

v WILLARD G. COOK. 

